Bug 1919040 - Allow choosing scales < 1.0 for SVG text. r=longsonr

This matches the previous behavior. The test in question has a
scale of 0.1 in the test, which changes our font choice and uses simpler
glyph advances.

Differential Revision: https://phabricator.services.mozilla.com/D222422

layout/svg/SVGTextFrame.cpp

@@ -367,10 +367,10 @@ static float GetContextScale(SVGTextFrame* aFrame) {
       RelativeTo{aFrame}, RelativeTo{SVGUtils::GetOuterSVGFrame(aFrame)});
   Matrix transform2D;
   if (!matrix.CanDraw2D(&transform2D)) {
-    return {};
+    return 1.0f;
   }
   auto scales = transform2D.ScaleFactors();
-  return std::max(1.0f, std::max(scales.xScale, scales.yScale));
+  return std::max(0.0f, std::max(scales.xScale, scales.yScale));
 }
 
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